一种抑制系统漏电流非隔离型三电平逆变器中点平衡载波调制算法

为了同时解决漏电流和中点平衡这两个问题,首先分析系统漏电流产生的机理以及传统调制策略对漏电流的影响,并且在大中零矢量调制(LMZVM)算法的基础上提出一种基于零序电压注入的大中正负小矢量调制(LMP/NSVM)算法。在非单位功率因数的情况下,根据直流侧中点总电荷量最小而选择LMP/NSVM或LMZVM策略,与大中小矢量调制(LMSVM)策略相比,本文提出的LMP/NSVM算法中点电位调节速度更快、稳态波动更小。系统漏电流与LMZVM基本相同并且优于传统的SVPWM,而且是基于载波思想实现的,算法简单、易于实现,因而该调制策略具有一定的工程应用价值。最后,与传统的三种调制策略实验结果对比,验证了理论分析的正确性与有效性。

A New Pulse-Width Modulation Algorithm for the Comprehensive Neutral-Point Balancing and Leakage Current Reducing in the Three-Level Transformerless Inverter

To reduce leakage current and balance neutral-point together, firstly analyzes the mechanism of leakage current of system and the effect of traditional modulation strategy on leakage current. And then based on the LMZVM carrier-based pulse width modulation, this paper proposes a carrier-based pulse-width modulation LMP/NSVM with zero-sequence voltage injection. Under the non-unity power-factor operation, this paper chooses the LMP/NSVM or LMZVM modulation strategy based on the dc side midpoint minimum charge. Compared with LMSVM modulation strategy, the NP potential is adjusted faster and the steady fluctuation is smaller using the LMP/NSVM proposed in this paper. The leakage current of the system is basically the same as the LMSVM and is better than the traditional SVPWM modulation strategy. And the algorithm from the angle of carrier-based pulse width modulation is extremely simple to realize. Eventually the effectiveness of the proposed modulation strategy is verified by comparing its results with traditional three modulation strategies.